The present invention is directed to stable aqueous detergent compositions which possess enhanced soil release properties.
The subject liquid detergent compositions contain carefully selected surface-active agents, hydrotropes, pH buffers and a soil-release copolymer. These ingredients are combined in to yield liquid detergent formulations that have excellent aesthetic as well as performance stability.
There is considerable reference in the literature to fomulations containing soil-release copolymers. The subject invention relates to only one type. This is a copolymer of ethylene terephtalate and polyethylene oxide terephthalate (EPT/PEOTP). More specifically it is a ETP/PEOTP copolymer with a rating of 1:1 to 9:1 and a molecular weight of about 500 to about 6,000 for the PEOTP and a total molecular weight of about 9,000 to 60,000. Examples of commercial products of this type are Zelcon 4780 (Dupont) and Milease T (ICI Americas). They are designed to give maximum soil-release when applied to 100% polyester fabric however, they also give some release properties to nylon, acetate and other synthetics.
The patent literature speaks to the difficulty of achieving performance (soil release) when the subject copolymers are incorporated into detergent formulations.
In U.S. Pat. No. 3,712,873 it is taught that copolymer release-agents such as used in this invention require special quaternary ammonium compounds plus special fatty alcohol ethoxylates (C.sub.16-22 +15-60 moles EO) to achieve performance. The present formulation are not compatible with the materials described and the alcohol ethoxylates described are not in the range one would select for good laundry detergency.
In U.S. Pat. No. 3,962,152 it is taught that performance is achieved by using a special copolymer considerably different in ETP/PEOTP ratio than that employed in the subject invention. The application is to granular detergents. The present soil-release agent is different and the composition is a liquid formulation.
U.S. Pat. No. 4,116,885 teaches that when using copolymers of the type preferred in the present invention a special component must be present to achieve performance. That component is 5-95% of the group consisting of C.sub.8-18 alcohol sulfate, C.sub.5-13 alcohol ethoxy (1-30 moles) sulfate and C.sub.14-20 alcohol ethoxy (4-30 moles) sulfate. Up to 10% of the total detergent used may be some other anionic detergent. Further it is taught that of the total anionic detergent level used 0-25% may be C.sub.8-18 LAS and/or C.sub.14-20 alcohol ethoxy (1-3 moles) sulfate.
The primary object of the present invention is therefor to provide a liquid detergent having soil-release properties and which is stable from separation and precipitation for extended periods of time.
It is a further object of the present invention to provide a method whereby soil release properties may be imparted to fabrics during normal laundering operations whereby upon subsequent soiling and laundering, soil is readily released.
These and other objects of the present invention will be apparent from the discussion which follows.